JPH11272029A - Image forming device - Google Patents

Abstract

(57) [Abstract] [Purpose] A tray for storing scattered and dropped toner itself has a heat insulating function so that the space occupied by members is reduced, and a high-quality image is stably obtained by preventing thermal deterioration of the toner. To provide an image forming apparatus capable of performing the above. A heat source including a fixing unit is disposed below an image forming unit including developing units, and a cover for collecting scattered and dropped toner is provided on the developing unit.
5M, 5C or an image forming apparatus provided below the developing rotary 5 and having a tray 71 for storing toner at the bottom of the cover 70, insulated so that the tray 71 can block heat generated from a heat source. Configure to be effective. According to the present invention, since the tray 71 itself exerts the heat insulating effect, a separate member exhibiting the heat insulating effect is not required, so that the space occupied by the member can be reduced, and the thermal deterioration of the toner can be prevented. A quality image can be obtained stably.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine or a printer employing an electrophotographic system or an electrostatic recording system.

[0002]

2. Description of the Related Art First, a conventional color laser printer will be outlined with reference to FIG.

Prior to forming a latent image, a charging roller 104b, which is a primary charger to which a voltage is applied, is pressed against a photosensitive drum 104a, which is an image carrier.
The surface of a is uniformly charged.

Exposure to the photosensitive drum 104a is performed by a scanner unit 110a having a laser diode. The laser diode emits light in response to an image signal, and the laser light is applied to a polygon mirror. Then, the polygon mirror is rotated at a high speed by the scanner motor to reflect the laser light, and the laser light reflected by the polygon mirror is combined with the coupling lens 110b and the reflection mirror 1
The outer peripheral surface of the photosensitive drum 104a is selectively exposed through 10c in accordance with an image signal. As a result, the photosensitive drum 1
An electrostatic latent image of each color is formed on the surface 04a by laser exposure.

On the other hand, the rotary developing device 105 includes developing devices for each color, that is, developing devices 105M, 105Y, 105C, and 10 having magenta, cyan, yellow, and black toners.
5B. These four-color developing units 105M, 1
05Y, 105C and 105B are arranged rotatably with respect to a shaft 105e, and each of the developing devices 105M, 105Y and 105B.
The center of C, 105B rotates in conjunction with the rotating gear disposed on the outer periphery of the revolving gear, and its posture is maintained constant.

In forming an image, developing units (105M, 105Y, 105C, 10C) corresponding to the latent images are used.
5B) stops at a position facing the photosensitive drum 104a,
Further, there, the developing sleeve 105b is moved to the photosensitive drum 104a.
Is positioned so as to face the surface of the device via a minute gap. Then, the developing devices (105M, 105Y, 105C,
105B) is connected to the high voltage power supply of the printer body when the developing sleeve 105b is rotated to the developing position, and the developing sleeve 105b performs a predetermined rotation while being coupled with the driving means from the driving source at the same time when the developing bias is applied. In this way, the latent image on the photosensitive drum 104a is developed by applying the bias and rotating the developing sleeve 105b at the time of development, and is visualized as a toner image.

On the other hand, a paper feed unit 101 is for feeding the transfer material 102 to the transfer drum 103, and is provided with a paper feed cassette 1 for storing the transfer material 102 loaded at the bottom of the apparatus main body.
01a. During image formation, the paper feed roller 101b rotates according to the image forming operation, and the paper feed cassette 101
a, the transfer material 102 is separated one by one from the
Feed to 03.

The transfer drum 103 wraps the transfer material 102 fed from the paper supply unit 101 to form a photosensitive drum 104a.
In order to transfer the toner images of the respective colors on the transfer material 102 at the transfer unit, the same speed V as the outer peripheral speed of the photosensitive drum 104a is used.
= 75.4 mm / sec (hereinafter referred to as process speed).

The transfer drum 103 has a diameter of 18 mm.
An elastic layer 103b is formed on the outer periphery of a 0 mm aluminum cylinder 103a with sponge, rubber, or the like, and a resistance layer 1 is formed on the outer periphery thereof.
03c is formed, and a dielectric layer 103d is formed on the outermost. At a predetermined position on the outer periphery of the transfer drum 103, a gripper 103f for gripping the leading end of the fed transfer material 102 is provided.
An electrostatic attraction roller 103g that can be separated from and attached to the outer periphery of the transfer drum 103 is provided on the outer periphery of the transfer drum 103 so as to sandwich the transfer material 102 between the transfer drum 103 and the outer periphery of the transfer drum 103.

When a voltage is applied between the suction roller 103f and the transfer drum 103, the transfer material 102, which is a dielectric, and the dielectric layer 103d of the transfer drum 103 are applied.
, And electrostatically attracts the transfer material 102 to the outer periphery of the transfer drum 103.

The cleaner 104d transfers the toner image to the transfer material 10
This is for cleaning the toner remaining on the photosensitive drum 104a after the transfer to No. 2, and is provided on the outer periphery of the photosensitive drum 104a downstream of the transfer section.

The fixing device 106 holds the transfer material 102 which holds the toner images of the respective colors and is peeled and conveyed from the transfer drum 103.
Is passed through the transfer material 102 to transfer the toner image of each color.
The fixing device includes a pressure roller 106a that is driven to rotate, and a fixing roller 106b that presses the roller 106a to apply heat and pressure to the transfer material 102.

The image forming operation includes a sheet feeding cassette 10
The transfer material 102 in 1a is fed to the transfer drum 103 by the paper feed roller 101b. The transfer drum 103 grips the leading end of the fed transfer material 102 with the gripper 103f and electrostatically attracts the transfer material to the peripheral surface thereof.

On the other hand, the photosensitive drum 104a, the surface of which is uniformly charged by the charging roller 104b, is provided with a scanner unit 110.
Exposure of the magenta image is performed from a, and a latent image of the magenta image is formed on the outer peripheral surface. Simultaneously with the formation of the latent image, the magenta developing device 105M is driven to apply a developing bias voltage having the same polarity and substantially the same potential as the charging polarity of the photosensitive drum 104a so that the magenta toner adheres to the magenta latent image formed on the photosensitive drum 104a. The latent image is developed by applying the voltage to obtain a magenta toner image on the photosensitive drum 104a. Then, a transfer potential having a polarity opposite to that of the magenta toner is applied to the transfer drum 103, and the magenta toner image on the photosensitive drum 104a is transferred to the transfer material 102 on the transfer drum 103.

When the transfer of the magenta toner image is completed, the next developing unit 105C rotates to rotate the photosensitive drum 104.
A full-color image is formed on the transfer material 102 by sequentially performing formation of a cyan, yellow, and black latent image, development, and transfer of the obtained toner image through a similar process through a similar process. .

The transfer drum 103, which grips and holds the transfer material 102, makes four rotations, so that
A full-color image of colors can be obtained. That is, 180
One full color is output in π × 4 / 75.4 = 30 seconds.

Transfer material 10 after transfer of four-color toner image is completed
2 is conveyed to a fixing device 106 after being separated from the transfer drum 103, and after the toner image is fixed by the fixing device 106, is discharged to a discharge tray 108 by a discharge roller pair 107.

[0018]

However, in the above-mentioned conventional image forming apparatus, a tray for collecting toner scattered at the time of image formation or toner dropped from the developing device and a cooling device for protecting the developing device from a rise in temperature are provided. Since the parts (airways) are arranged, there is a problem that a large space is required for installing these parts.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems. An object of the present invention is to reduce the space occupied by members by making the tray for storing scattered and dropped toner itself also have a heat insulating function, and to reduce the space occupied by the members. An object of the present invention is to provide an image forming apparatus capable of stably obtaining a high-quality image while preventing thermal deterioration of the image forming apparatus.

[0020]

According to the first aspect of the present invention, a heat source including a fixing unit is disposed below an image forming unit including a developing unit to collect scattered and dropped toner. An image forming apparatus having a cover below the developing device or a rotary for fixing the developing device, and a tray for storing toner at the bottom of the cover, the tray blocking heat generated from a heat source. It is characterized in that it is configured to exhibit a heat insulating effect as much as possible.

According to a second aspect of the present invention, in the first aspect of the present invention, the tray forms an air passage, and the air layer in the air passage exerts a heat insulating effect.

According to a third aspect of the present invention, in the first aspect of the present invention, a heat insulating sheet is attached to an outer peripheral surface of the tray.

According to a fourth aspect of the present invention, the tray has a thermal conductivity λ of 1 × 10 ⁻⁶ ≦ λ ≦ 2.5 × 10 ⁻⁴ [cal / cm · sec.
・ ° C]).

Therefore, according to the present invention, since the tray itself for storing the scattered and dropped toner is made to exhibit the heat insulating effect, a separate member for exhibiting the heat insulating effect becomes unnecessary, and the space occupied by the member can be reduced. ,
Thermal deterioration of the toner is prevented, and a high-quality image can be stably obtained.

[0025]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

First Embodiment [Overall Configuration of Image Forming Apparatus] First, the overall configuration of a color image forming apparatus will be outlined with reference to FIG.

FIG. 1 is a cross-sectional view of a main part of a color laser printer as an embodiment of a color image forming apparatus. The color laser printer includes a photosensitive drum 1 as an image carrier rotating at a constant speed and a fixed black developing device. Container 4 and rotatable 3
An image forming unit including one color developing unit 5Y, 5M, 5C, and a color image developed and multi-transferred in the image forming unit, and further transferred to a transfer material fed from a feeding unit. And an intermediate transfer member 6.

The transfer material on which the color image has been transferred is conveyed to the fixing unit 10 and after the color image is fixed,
The sheet is discharged to a discharge section on the upper surface of the apparatus by a discharge roller.
The rotatable color developing devices 5Y, 5M, 5C and the fixed black developing device 4 are configured to be individually detachable from the printer main body.

Next, the structure of each part of the color laser printer will be described in detail.

[Image Carrier Unit] Drum Unit 7
Is formed integrally with the photosensitive drum 1 and a container 7b of a cleaning device which also serves as a holder for the photosensitive drum 1,
The drum unit 7 is detachably supported by the printer main body, and is configured to be easily replaceable according to the life of the photosensitive drum 1. The photosensitive drum 1 according to the present embodiment is configured by applying an organic photoconductor layer to the outside of an aluminum cylinder having a diameter of about 60 mm, and is rotatably mounted on a container 7b of a cleaning device also serving as a holder for the photosensitive drum 1. Supported.

On the periphery of the photosensitive drum 1, a cleaner blade and a primary charging means 2 are arranged, and the photosensitive drum 1 is driven by a driving force transmitted from a driving motor (not shown) arranged on the back side of FIG. Is driven to rotate in the direction shown by the arrow (counterclockwise) in accordance with the image forming operation.

[Charging Means] The primary charging means 2 employs a contact charging method, in which a conductive roller is brought into contact with the photosensitive drum 1 and a voltage is applied to the conductive roller to thereby charge the photosensitive drum. 1 to uniformly charge the surface.

[Exposure Means] Exposure to the photosensitive drum 1 is performed from a scanner unit 3. That is, when an image signal is given to the laser diode, the laser diode irradiates the polygon mirror 3a with image light corresponding to the image signal. The polygon mirror 3a is rotated at a high speed by a scanner motor, and the image light reflected by the polygon mirror 3a is exposed by selectively exposing the surface of the photosensitive drum 1 rotating at a constant speed via the imaging lens 3b and the reflection mirror 3c. An electrostatic latent image is formed on the drum 1.

[Developing Means] The developing means includes three rotations for developing each color of yellow, magenta, cyan and black in order to visualize the electrostatic latent image formed on the photosensitive drum 1. It is composed of developing units 5Y, 5M, 5C and one black developing unit 4.

The black developing device 4 is a fixed developing device, and its developing sleeve 4a is arranged at a position facing the photosensitive drum 1 at a minute interval (about 300 μm) with respect to the photosensitive drum 1. A visible image is formed by toner.

The black developing device 4 feeds the toner in the container by the feed mechanism, and the toner is applied to the outer periphery of the developing sleeve 4a which rotates in the direction shown by the arrow (clockwise) by a coating blade pressed against the outer periphery of the developing sleeve 4a. The toner is applied in a thin layer, and a charge is applied to the toner (frictional charging).
Then, by applying a developing bias to the developing sleeve 4a, toner development is performed corresponding to the electrostatic latent image on the photosensitive drum 1.

On the other hand, three rotary developing devices 5Y, 5M, 5C
Are detachably held by a developing rotary 5 that rotates about a shaft 5d. When forming an image, the developing units 5Y, 5M, and 5C rotate about the shaft 5d while being held by the developing rotary 5. , A predetermined developing device (5Y,
5M, 5C) stops at a position facing the photosensitive drum 1,
Further, after the developing sleeve 5a is positioned so as to correspond to the photosensitive drum 1 at a minute interval (about 300 μm), a visible image is formed corresponding to the electrostatic latent image on the photosensitive drum 1.

When a color image is formed, the developing rotary 5 rotates for each rotation of the intermediate transfer member 6, and the yellow developing device 5 rotates.
The developing process is performed in the order of Y, magenta developing device 5M, cyan developing device 5C, and then black developing device 4. FIG. 1 shows a state in which the yellow rotary developing device 5Y is positioned at a position facing the photosensitive drum 1 and is stationary.

The rotary developing device 5Y feeds the toner in the container to the coating roller 5b by a feeding mechanism, and rotates clockwise in the drawing by the coating roller 5b rotating clockwise in the drawing and the blade 5c pressed against the outer periphery of the developing sleeve 5a. A thin layer of toner is applied to the outer periphery of the developing sleeve 5a to be charged, and a charge is applied to the toner (frictional charging). Then, a developing sleeve 5 corresponding to the photosensitive drum 1 on which the latent image is formed
By applying a developing bias to “a”, toner development is performed on the photosensitive drum 1 according to the latent image. The magenta developing device 5M and the cyan developing device 5C also perform toner development by the same mechanism as described above.

The developing sleeves 5a of the rotary developing devices 5Y, 5M, 5C are connected to the high-voltage power supplies for color development provided in the printer body when the developing devices 5Y, 5M, 5C are rotated to the developing positions. And the drive, and the drive is connected by sequentially and selectively applying a voltage for each color development.

[Intermediate Transfer Body] The intermediate transfer body 6 transfers the toner image on the photosensitive drum 1 visualized by the developing units 4, 5Y, 5M and 5C four times (yellow (Y), In order to receive multiple transfer over magenta (M), cyan (C), and black (B) images, the photosensitive drum 1 rotates in the clockwise direction in synchronization with the outer peripheral speed of the photosensitive drum 1. The transferred intermediate transfer body 6 sandwiches the transfer material with the transfer roller 8b to which a voltage is applied and transports the transfer material, thereby simultaneously multiple-transferring the respective color toner images on the intermediate transfer body 6 to the transfer material. .

The intermediate transfer member 6 according to the present embodiment is
A 180-mm-diameter aluminum cylinder is formed by covering the outer periphery with an elastic layer 6a such as a medium-resistance sponge or medium-resistance rubber. The intermediate transfer body 6 is rotatably supported and temporarily fixed (not shown). Rotates under the driving force from
Also, it can be easily attached and detached.

[Cleaning Unit] The cleaning unit cleans the toner remaining on the photosensitive drum 1 after the toner visualized on the photosensitive drum 1 is transferred to the intermediate transfer member 6 by the developing unit. The cleaned waste toner is stored in the cleaner container 7b.
The amount of waste toner stored in the cleaner container 7b does not fill the cleaner container 7b earlier than the life of the photosensitive drum 1, and therefore, the cleaner container 7b is integrally and simultaneously replaced when the life of the photosensitive drum 1 is replaced.

[Sheet Feeding Unit] The sheet feeding unit feeds the transfer material to the image forming unit, which includes a sheet feeding cassette containing a plurality of transfer materials, a sheet feeding roller, a feeding roller, and a double feeding. It mainly comprises a retard roller for prevention, a paper feed guide, and a registration roller roller 26.

During image formation, the paper feed roller is driven and rotated in accordance with the image forming operation, the transfer materials in the paper feed cassette are separated and fed one by one, and the transfer materials are transported while being guided by the guide plate. Registration roller 2 via roller
To 6. During the image forming operation, the registration roller 26 performs a non-rotational operation of causing the transfer material to stand still and
Is performed in a predetermined sequence, and the position of the image and the transfer material at the time of the transfer process, which is the next process, is aligned.

[Transfer Section] The transfer section is constituted by a swingable transfer roller 8b. This transfer roller 8b is constructed by winding a metal shaft with a medium-resistance foam elastic body, and is movable up and down in FIG. is there.

While the four-color toner image is being formed on the intermediate transfer member 6, that is, while the intermediate transfer member 6 rotates a plurality of times, the broken lines are shown in FIG. As shown, the transfer roller 8b is located below and separated from the intermediate transfer body 6. After the formation of the four color toner images on the intermediate transfer member 6, the transfer roller 8b is moved upward by a cam member (not shown) as a solid line in FIG. Is pressed to the intermediate transfer body 6 with a predetermined pressure via the transfer material. At this time, a bias is simultaneously applied to the transfer roller 8b, and the toner image on the intermediate transfer body 6 is transferred to the transfer material. Here, since the intermediate transfer body 6 and the transfer roller 8b are driven respectively, the transfer material sandwiched between the two is subjected to a transfer process and at the same time, toward the fixing device 10 in the leftward direction in FIG. Transported at a speed of

[Intermediate Transfer Member Cleaning Unit] The intermediate transfer member cleaning member 9 includes a charging roller 9a, an electrode (not shown) for supplying power to the charging roller 9a, a holder 9b for holding these members, and a predetermined cleaning member 9. It comprises a cam mechanism (not shown) for bringing the intermediate transfer body 6 into contact with / separating from the intermediate transfer body 6 at a timing and a spring (not shown) for forming a nip at the time of contact.

The charging roller 9a is formed by winding a metal shaft with a medium-resistance elastic body, and swings around a single axis of rotation (not shown) of the holder 9b while being held by the holder 9b.

The cleaning member 9 during image formation on the photosensitive drum 1 and primary transfer to the intermediate transfer body 6 (before secondary transfer starts) is separated by a cam (not shown).
The rotation of the charging roller 9a and the power supply to the charging roller 9a are not performed. For this reason, when forming a full-color image, four colors, that is, yellow, magenta, cyan, and black toners can be superimposed and primary-transferred onto the intermediate transfer body 6 without disturbing the primary-transferred image.

The cleaning member 9 is released from the intermediate transfer body 6 after the secondary transfer at a predetermined timing by a cam (not shown), and the charging roller 9a comes into contact. The operation of the cam realizes a smooth operation of the cleaning member 9 at the time of contact with and separation from the intermediate transfer member 6, and alleviates a shock at the time of contact / separation with the intermediate transfer member 6, and adversely affects image formation. I try to relax. Since the contact pressure f for nip formation is sufficiently lower than the contact pressure F of the intermediate transfer member 6 to the photosensitive drum 1, the charging roller 9a is
, The fixing position of the intermediate transfer member 6 does not change or bend due to the contact pressure. In the present embodiment, good cleaning is realized when f = 500 g and F = 5 kg.

As described above, the contacting charging roller 9a rotates following the intermediate transfer member 6 by the frictional force with the intermediate transfer member 6, so that the outer peripheral speed of the charging roller 9a is
And the constant speed is always maintained even if an error occurs in the outer diameter due to the accuracy of the parts. At this time, the photosensitive drum 1 is brought into contact with the nip between the charging roller 9a and the intermediate transfer member 6.
The toner is charged to the opposite polarity to the charge polarity of the toner above, and is simultaneously reverse-transferred from the intermediate transfer body 6 to the photosensitive drum 1 at the time of the next primary transfer (primary transfer of the next color in the case of full color) in the primary transfer section. The waste toner that is cleaned from the photosensitive drum 1 by the cleaning unit and removed by the cleaning is collected in the cleaner container 7b.

[Fixing Device] The fixing device 10 fixes the toner image formed on the transfer material via the intermediate transfer member 6 to the toner image formed by the developing means.
As shown in FIG. 1, a fixing roller 1 for applying heat to a transfer material
0a and a pressure roller 10b for pressing the transfer material against the fixing roller 10a.
Reference numeral 10b denotes a hollow roller, each of which has a heater therein, and conveys the transfer material while being rotated and driven.

That is, the transfer material holding the toner image undergoes fixing of the toner image by applying heat and pressure in the process of being conveyed by the fixing roller 10a and the pressure roller 10b.

[Image Forming Operation] Next, an image forming operation of the color laser printer configured as described above will be described.

First, the paper feed roller of the paper feed unit is rotated to separate one transfer material in the paper feed cassette and transport it to the registration roller 26.

On the other hand, the photosensitive drum 1 and the intermediate transfer member 6 rotate at the outer peripheral speed V of 75.4 mm / sec (hereinafter, referred to as process speed) in the direction indicated by the arrow. The photosensitive drum 1 having a diameter of 60 mm rotates once in 60π / 75.4 = 2.5 seconds,
180 π / 75.4 = intermediate transfer member 6 having a diameter of 180 mm
One rotation in 7.5 seconds. Further, since the photosensitive drum 1 and the intermediate transfer body 6 are connected by a gear (not shown), when the photosensitive drum 1 makes three rotations, the intermediate transfer body 6 makes one full rotation.

When an arbitrary point on the outer periphery of the intermediate transfer member 6 reaches the position S shown in the figure, the photosensitive drum 1 whose surface is uniformly charged by the charging means 2 is exposed to the laser at the position E shown in the figure. Then, image formation is performed. The distance a from the exposure position E of the photosensitive drum 1 to the contact portion T1 with the intermediate transfer member 6 in the counterclockwise direction is equal to the distance b from the illustrated point S of the intermediate transfer member 6 to the contact portion T1. The point E at which writing of the image starts and the point S on the intermediate transfer member 6 coincide at the position of the contact portion T1. That is, an image is formed counterclockwise with respect to the intermediate transfer body 6 with the point S as a tip.

1) Formation of yellow image: scanner section 3
To form a yellow latent image on the photosensitive drum 1. Simultaneously with the formation of the latent image, the yellow developing unit 5Y is driven to apply a voltage having the same polarity and substantially the same potential as the charging polarity of the photosensitive drum 1 so that the yellow toner adheres to the latent image on the photosensitive drum 1, thereby performing yellow developing. I do. At the same time, the yellow toner image on the photosensitive drum 1 is primarily transferred to the outer periphery of the intermediate transfer member 6 at a first transfer position T1 slightly downstream of the developing section. At this time, the primary transfer is performed by applying a voltage having a characteristic opposite to that of the yellow toner to the intermediate transfer body 6.

When the image to be formed is A3 size, it is 420 mm in length, and is L1 from the point S on the outer periphery of the intermediate transfer member 6.
An image is formed up to the point. When the transfer of the yellow toner image to the intermediate transfer member 6 is completed (that is, when the point L1 has passed the first transfer position T1), the developing rotary 5 rotates clockwise, and the next magenta developing device 5M rotates. It moves and is positioned at a position facing the photosensitive drum 1 and stops.

2) Formation of magenta image: Next, when the point S (the leading end of the yellow image) on the outer periphery of the intermediate transfer member 6 makes one round and is located again at the point S, the laser of the magenta image is similarly scanned by the scanner section 3. Irradiation is started, a magenta toner image is developed on the latent image on the photosensitive drum 1 in the same manner as for yellow, and the magenta toner image on the photosensitive drum 1 is similarly transferred onto the intermediate transfer body 6 at the first transfer position T1. You. When the transfer of the magenta toner image to the intermediate transfer member 6 is completed (that is, when the point L1 has passed the first transfer position T1),
The developing rotary 5 rotates clockwise, and the next cyan developing device 5M rotates and moves to the position facing the photosensitive drum 1 and stops.

3) Formation of cyan image: Next, a point S on the outer periphery of the intermediate transfer member 6 (the tip of the yellow and magenta images)
Is rotated once again and is located at the point S, similarly, the laser irradiation of the cyan image is started by the scanner unit 3 and the cyan toner image is developed into the latent image on the photosensitive drum 1 in the same manner as magenta. 1 is the first cyan toner image
At the transfer position T1, the toner image is transferred onto the intermediate transfer member 6 so as to be superimposed on the yellow and magenta toner images. When the transfer of the cyan toner image to the intermediate transfer member 6 is completed (that is, when the point L1 has passed the first transfer position T1), the developing rotary 5 rotates clockwise by an angle of 60 ° and faces the photosensitive drum 1. The color developing devices 5Y, 5M, 5C do not exist at the positions indicated.

4: Formation of black image: Next, when the point S (the end of the yellow / magenta / cyan image) on the outer periphery of the intermediate transfer member 6 makes another round and is located again at the point S, the scanner unit 3 Starts the laser irradiation of the black image, and then the black toner image is developed by the black developing device 4, and the black toner image on the photosensitive drum 1 is further transferred onto the intermediate transfer body 6 at the first transfer position T1. .

The latent image formation, development and transfer of the toner image to the intermediate transfer member 6 are sequentially performed four times in the order of yellow, magenta, cyan, and black, so that yellow, magenta, A full-color image composed of four kinds of toners of cyan and black is formed.

Before the transfer of the black toner image to the intermediate transfer member 6 is completed (that is, the intermediate transfer member 6 on which the first transfer of the fourth black toner image is completed to form a full-color image)
(Before the leading edge S of the image reaches the second transfer portion T2), the transfer material, which has been waiting by the registration roller 26, is started to be transported at an appropriate timing.

When the image of each color is formed on the intermediate transfer member 6 four times, the image forming apparatus waits downward, and simultaneously moves the transfer roller 8b, which has not been in contact with the intermediate transfer member 6, upward by a cam (not shown). And the transfer material is transferred to the second transfer portion T of the intermediate transfer body 6.
By applying a bias having the reverse characteristic to that of the toner to the transfer roller 8b at the same time as the pressure contact at 2, the full-color image on the intermediate transfer body 6 is simultaneously transferred to the transfer material in four colors at a stretch.

The transfer material having passed through the second transfer portion T2 is peeled off from the intermediate transfer member 6 and conveyed to the fixing device 10, where the full color image is fixed in the fixing device 10, and then the discharge roller pair. As a result, the image is discharged onto the discharge tray in the upper part of the main body with the image surface facing downward, and a series of image forming operations ends here.

Next, the gist of the present invention will be described.

As shown in FIG. 1, in an image forming apparatus in which a portion related to image formation such as a developing rotary 5 is disposed above a heat source such as a fixing device 10, the developing devices 5Y, 5M, 5C
Tray 7 for storing toner scattered or dropped from
1 and the developing devices 5Y, 5M, 5C from the heat generated from the heat source.
A heat insulating portion (air passage 75) for preventing a rise in temperature in the periphery is separately arranged. In this configuration, a space for arranging both the tray 71 and the air path 75 must be secured.

Therefore, if the tray 71 for storing the scattered or dropped toner can be provided with a heat insulating effect so as to block the heat generated from the heat source, the structure can be simplified and the space can be reduced. Can be suppressed.

For example, as shown in FIG. 2, a tray 7 provided at the bottom of a cover 70 covering the developing rotary 5
It is conceivable that the bottom of the tray 71 has a raised shape so that the gap 72 is formed when the device 1 is placed on a plane. Since a heat insulating layer is formed by flowing outside air through the gap 72, the tray 71 can be provided with a heat insulating effect. As a result, the configuration of the apparatus can be simplified and the space can be reduced. Can be.

As shown in FIG. 3, the outside air 75 flowing through the gap 72 is taken in from a slit-like air inlet formed in a front cover (not shown), and an exhaust fan 76 disposed on the rear plate 77 side of the main body. The air may be exhausted outside the machine.

According to the present embodiment, the temperature around the developing units 5Y, 5M, 5C can be suppressed to about 50 ° C. to about 40 ° C. in the full-color continuous printer mode.
In addition, even during standby, the temperature, which was
It could be suppressed to 6 to 37 ° C. in this way,
By suppressing the temperature rise around the developing devices 5Y, 5M, and 5C, thermal deterioration of the toner can be prevented, and a stable image can be output.

Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a cross-sectional view of a main part of an image forming apparatus according to Embodiment 2 of the present invention. In FIG. 4, the same elements as those shown in FIG.

In this embodiment, a heat insulating sheet 73 is attached to the outer peripheral portion of a rectangular parallelepiped tray 71 for collecting toner. In addition, as the heat insulating sheet 73, for example, a heat insulating felt having a thickness of about 1 mm is desirable. In addition, a polyphenylene sulfide film is also effective.

As described above, two kinds of materials are used by attaching the heat insulating sheet 73 to the outer peripheral portion of the tray 71, but the tray 71 having a heat insulating effect can be formed. Thus, the first embodiment
The same effect as described above can be obtained.

Third Embodiment Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 5 is a sectional view of a main part of the image forming apparatus according to Embodiment 3 of the present invention. In this figure, the same elements as those shown in FIG. 2 are denoted by the same reference numerals.

In the present embodiment, the tray 74 is made of a material having excellent heat insulating properties so as to provide the tray 74 with high heat insulating properties. The same effect can be obtained.
In addition, the material having excellent heat insulating properties referred to herein has a thermal conductivity λ of 1 × 10 ⁻⁶ ≦ λ ≦ 2.5 × 10 ⁻⁴ [cal / cm · sec · ° C.]. A material, for example, a heat insulating material based on an inorganic fiber obtained by mixing a ceramic fiber and a glass fiber is effective.

[0079]

As is apparent from the above description, according to the present invention, the tray itself for storing the scattered and dropped toner exerts the heat insulating effect, so that a separate member exhibiting the heat insulating effect becomes unnecessary. The space occupied by the members can be kept small, and thermal deterioration of the toner can be prevented, so that a high-quality image can be stably obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part of an image forming apparatus (color laser printer) to which the present invention is applied.

FIG. 2 is a sectional view of a main part of the image forming apparatus according to Embodiment 1 of the present invention.

FIG. 3 is a perspective view of a tray portion of the image forming apparatus according to Embodiment 1 of the present invention.

FIG. 4 is a sectional view of a main part of an image forming apparatus according to Embodiment 2 of the present invention;

FIG. 5 is a sectional view of a main part of an image forming apparatus according to Embodiment 3 of the present invention.

FIG. 6 is a sectional view of a conventional color laser printer.

[Explanation of symbols]

 Reference Signs List 1 photosensitive drum 5 developing rotary 5Y, 5M, 5C developing device 10 fixing device 70 cover 71, 74 tray 72, 75 air passage 73 heat insulating sheet

Claims (4)

[Claims] A heat source including a fixing device is disposed below an image forming section including a developing device, and a cover for collecting scattered and dropped toner is provided below the developing device or a rotary for fixing the developing device. An image forming apparatus comprising a tray for storing toner at the bottom of the cover, wherein the tray has a heat insulating effect so as to block heat generated from a heat source. . 2. The image forming apparatus according to claim 1, wherein the tray forms an air passage, and a heat insulating effect is exerted by an air layer in the air passage. 3. The image forming apparatus according to claim 1, wherein a heat insulating sheet is attached to an outer peripheral surface of said tray. 4. The tray according to claim 1, wherein the thermal conductivity λ is 1 × 10 ⁻⁶ ≦
2. The image forming apparatus according to claim 1, wherein the image forming apparatus is made of a material satisfying λ ≦ 2.5 × 10 ⁻⁴ [cal / cm · sec · ° C.]).